Method and apparatus for spinal fixation

ABSTRACT

A spinal fixation implant system for correction and fixation of the human spine to facilitate an anatomically correct fusion. The spinal fixation system may include a connector, a spinal rod, a spinal fixation component, a sleeve, and a fastener. The spinal fixation component preferably includes a fixation device such as a hook or screw for securing the spinal rod to vertebrae of the thoracic or lumbar spine. The spinal fixation component preferably includes a threaded end on its top that is adapted to receive the fastener. The fixation component may include a body having a tapered cavity for engaging the receiving end of the connector. Tightening of the fastener preferably downwardly translates the sleeve over the fixation component body to force the connector through the tapered cavity, which compresses the receiving end about the spinal rod to fixably connect the spinal rod and the spinal fixation component. In an alternate embodiment, assembly pliers may be used to move the connector into the tapered cavity. The fixation component may also include a rotatable fixation member. The spinal rod and connector may include a textured surface to inhibit movement of the connector with respect to the spinal rod. The fastener may be a clip configured to engage an indentation formed in the connector to secure the connector within the fixation component. The connector may include a tab which is configured to interact with a channel formed in the cavity to inhibit the removal of the connector from the cavity.

This application is a divisional application of Ser. No. 09/026,711filed on Feb. 26, 1998, now U.S. Pat. No. 5,989,250, which is acontinuation-in-part of U.S. patent application Ser. No. 08/942,325filed on Oct. 1, 1997 which is a continuation-in-part of U.S. patentapplication Ser. No. 08/740,123 filed on Oct. 24, 1996 now U.S. Pat. No.6,416,515.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to spinal fixation systems andthe like. More particularly, an embodiment of the invention relates to aspinal implant system for correction, fixation, and stabilization of thehuman spine to allow the development of a solid spinal fusion.

2. Description of the Related Art

Spinal fixation, such as lumbar sacral fusion and the correction ofspinal deformities such as scoliotic curves, is a well known andfrequently used medical procedure. Pedicle, lateral, and obliquemounting devices may be used to secure corrective spinal instrumentationto a portion of the spine that has been selected to be fused byarthrodesis.

A spinal fixation system typically includes corrective spinalinstrumentation that is attached to selected vertebrae of the spine byscrews, hooks, and clamps. The corrective spinal, instrumentationincludes spinal rods or plates that are generally parallel to thepatient's back. The corrective spinal instrumentation may also includetransverse connecting rods that extend between neighboring spinal rods.Spinal fixation systems are used to correct problems in the lumbar andthoracic portions of the spine, and are often installed posterior to thespine on opposite sides of the spinous process and adjacent to thetransverse process.

Various types of screws, hooks, and clamps have been used for attachingcorrective spinal instrumentation to selected portions of the patient'sspine. Examples of pedicle screws and other types of attachments areillustrated in U.S. Pat. Nos. 4,763,644; 4,805,602; 4,887,596;4,950,269; and 5,129,388. Each of these patents is incorporated byreference as if fully set forth herein.

An eyebolt assembly of the TSRH® spinal system sold by Danek MedicalInc. is illustrated in FIG. 1. The eyebolt assembly 2 encircles spinalrod 4 such that assembly mass completely surrounds the spinal rod. Thespinal rod must be inserted through the eyebolt, which rests within theyoke of spinal hook 8. The spinal hook attaches the spinal rod to a bonyelement of the spine. A nut 6 is threaded onto a post of the eyeboltassembly to fixably secure the rod within the yoke. The nut is tightenedso that the assembly resists axial, torsional, and shear forces toinhibit motion of the spinal rod relative to the assembly in thedirections indicated by the arrows in FIG. 1. Further details of theTSRH® spinal system are provided in the TSRH® Spinal Implant SystemSurgical Technique Manual and the TSRH® Crosslink Surgical TechniqueManual. Both of these publications are available from Danek Medical Inc.and are incorporated by reference as if fully set forth herein.

Manual insertion of a spinal rod through the bores of a number ofspaced-apart eyebolts within a surgical wound tends to be difficult. Thebore axis of each eyebolt must be properly aligned along a common axis,which is difficult since the corrective procedure requires that thespinal rod initially be placed under stress to resist deforming forcesof the spine. Therefore, the use of systems such as the TSRH® spinalsystem may require that a predetermined number of screws or hooks bepre-loaded onto the spinal rod in a particular order and spacing priorto the insertion of the spinal rod into the surgical wound. Afterinsertion of the spinal system into the surgical wound, however, it isoften necessary to add, delete, or reposition one or more hooks orscrews. Before such modifications can be made, the spinal systemtypically must be removed from the surgical wound and at least partiallydisassembled.

To overcome such problems, some spinal fixation systems include “openback” hooks or screws to allow a spinal rod to be dropped into the openback of the hook or screw and secured within the open back by a separatecomponent and a set screw. Such a system is illustrated in U.S. Pat. No.5,102,412 to Rogozinski, which is incorporated by reference as if fullyset forth herein. Such systems tend to be susceptible to fatigue stressfailure and require assembly within the surgical wound. In addition,adding a hook or screw to the construct tends to require that the spinalrod first be repositioned. A further disadvantage of this approach isthat component mass completely surrounds the spinal rod, resulting in anincrease in the profile width of the device and greater impingement ofthe device upon the fusion mass. A low profile width is generallydesired to minimize sinus formation and soft tissue irritation fromhardware prominence.

U.S. Pat. No. 5,242,445 to Ashman relates to a “split eyebolt” assemblyfor adding eyebolts to an assembled spinal fixation construction.Attaching the split eyebolt to a spinal rod requires a special crimpingtool to crimp the split eyebolt over the rod. The crimping tool tends tobe difficult to operate within the surgical wound. Furthermore, thethreads of the opposing sides of the split eyebolt are often misalignedafter crimping, making it difficult or impossible to thread a nut ontothe split eyebolt. The split eyebolt also completely encircles thespinal rod thereby increasing the impingement of the construct upon thefusion mass.

It is therefore desirable that an improved spinal fixation system bederived that facilitates assembly and surgical implantation by allowingthe spinal rod to be positioned within the surgical wound (a) after thefixation components (e.g., screws, hooks) have been implanted, (b)without modifying the fixation components, and (c) whereby fixationcomponents may be subsequently added, deleted, and/or repositionedwithout disassembling the system.

SUMMARY OF THE INVENTION

In accordance with the present invention, a spinal fixation system isprovided that largely eliminates or reduces the aforementioneddisadvantages of conventional spinal fixation constructions. Anembodiment of the invention relates to an implant system for fixation ofthe human spine that includes a spinal rod, a fixation component, aconnector, and a fastener.

The connector may be used to connect the spinal rod to the fixationcomponent and preferably includes a receiving end and a fastening end.The receiving end may contain a first arm and a second arm that togetherform a substantially U-shaped borehole into which the spinal rod may beaxially positioned. The receiving end preferably surrounds only part ofthe spinal rod such that the unsurrounded portion of the spinal rod isexposed from the borehole. The exposed portion of the spinal rod mayextend out of an open end of the U-shaped borehole. The spinal rod maybe circular and preferably includes a cross-section having acircumferential portion. The receiving end of the connector preferablysurrounds and engages greater than about π radians and less than about 2π radians of the circumferential portion.

The receiving end of the connector preferably acts as a “pinch clamp” byexerting a clamping force on opposing sides of the spinal rod to securethe spinal rod within the borehole. The connector preferably contains aslot between the receiving end and the fastening end that enables thefirst arm and the second arm to be deflected relative to one another.The deflection of the arms allows the distance between a tip of thefirst arm and a tip of the second arm to be changed so that the spinalrod may be inserted through an open end of the U-shaped borehole that isdefined between the tips of the arms.

The fixation component preferably includes a fixation device such as abone screw or hook for engaging vertebrae of the thoracic or lumbarspine. The fixation component also preferably includes a body containinga cavity with an inner surface. The cavity is preferably sized toreceive a portion of the connector. The connector is preferablypartially disposed within the cavity such that at least a portion of thefastening end extends from the cavity, whereby the inner surface of thecavity engages an outer surface of the receiving end. The cavity of thebody is preferably a tapered cavity that narrows in a direction from afirst end of the cavity to a second end of the cavity. The taperedcavity preferably surrounds a portion of the receiving end and imparts acompressive force against the receiving end to secure the spinal rodwithin the borehole.

The fastener preferably engages both the body and the portion of thefastening end that extends from the cavity. The fastener may secure theconnector and the fixation component together. The fastener ispreferably a nut adapted to be threaded upon the fastening end. Thefastener may be selectively tightened to allow an engagement between theconnector and the spinal rod that may be overcome by the application ofa distraction force to the connector. Rotation of the nut in atightening direction about the fastening end preferably draws a portionof the receiving end through the tapered cavity, causing the innersurface of the cavity to compress the arms of the receiving end. Inturn, the arms may exert a compressive force against the spinal rod toclamp it within the borehole. The magnitude of the compressive forceagainst the spinal rod preferably varies as a function of the degree towhich the nut is tightened. The open end of the U-shaped boreholepreferably has a width that can be adjusted by tightening the fastener.

The fixation component may include a spacer located between the fastenerand the spinal rod for laterally offsetting the fixation device aselected lateral distance from the spinal rod. The spacer may include asurface having a plurality of radially-spaced teeth. The fixationcomponent may comprise a plurality of radially-spaced protrusionsadapted to fit adjacent to the teeth on the surface of the spacer. Thetightening of the nut preferably causes the spacer and the fixationcomponent to become pressed together such that a complementaryengagement between the teeth of the spacer and the protrusions of thefixation device is formed to inhibit rotation of the fixation deviceabout the spacer.

The body may include a U-shaped yoke formed between a top section and abottom section that each have an edge adjacent to the yoke. The taperedcavity preferably is formed between the top section and the bottomsection and extends in a perpendicular direction relative to theU-shaped yoke. The fixation component is preferably adapted to pivotabout the spinal rod in a substantially vertical plane. The edges of thetop and bottom sections preferably contact the spinal rod during thepivoting of the fixation component to define the range of pivotal motionof the fixation component about the spinal rod. The edges are preferablycurved in a direction away from the spinal rod to increase the range ofpivotal motion of the fixation component.

The fixation component may include a transverse connector to maintain afixed distance between the spinal rod and a neighboring spinal rod. Thetransverse connector may include a reduced section that has a width lessthan that of the body, allowing the reduced section to be more easilybent. The reduced section may be bent to shorten the lateral distancebetween the spinal rod and an adjacent spinal rod. The transverseconnector may contain a beveled section between the body and the reducedsection.

In an embodiment, the connector includes a receiving end forming asubstantially U-shaped borehole and a capped end opposite the receivingend. The connector may be forced into the cavity of a fixation componentbody with an instrument such as a pair of assembly pliers. Theinstrument preferably includes a first elongated member and a secondelongated member. The elongated members may be moved relative to oneanother to exert a compressive force against the connector and thefixation component to move the connector within the cavity of thefixation component body. The first elongated member preferably includesa curvate indention for engaging the spinal rod. The second elongatedmember preferably includes a borehole for receiving an end of theconnector.

In an embodiment, the fixation component includes a fastening end. Thefastening end preferably is adapted to receive a fastener (e.g.,threaded nut). Downward translation of the fastener preferably moves asleeve downwardly over the body of the fixation component. The sleevepreferably contains a substantially U-shaped opening having a angledlocking surface for engaging the spinal rod. During assembly, thefastener is preferably tightened to move the sleeve downwardly, therebyimparting a force on the spinal rod that causes the connector to movethrough the tapered cavity.

In an embodiment, the fixation component may include a pivotablefixation device. The fixation device is preferably adapted to pivotabout the body of the fixation component along the longitudinal axis ofthe body. The body of the fixation component may be adapted to inhibitthe lateral motion of the fixation device. The body of the fixationcomponent may be adapted to engage a portion of the connector.

In an embodiment the connector may include an opening adapted tocompletely surround the circumferential portion of the spinal rod. Theconnector may include a slot running through the center of theconnector, communicating with the opening. The slot may be adapted toallow the circumference of the opening to vary. Insertion of a spinalrod preferably causes the slot to widen such that the circumference ofthe opening increases. The connector may be placed within the fixationcomponent such that the slot is narrowed to secure a spinal rod to theconnector.

In an embodiment, movement of the connector with respect to the spinalrod may be further inhibited by texturing either the surface of thespinal rod or the inner surface of the connector (i.e., the surface ofthe connector that contacts the spinal rod). Preferably, both surfacesare textured to inhibit movement of the connector with respect to thespinal rod. A number of textured surfaces may be used to increase thecoefficient of friction between the inner surface of the connector andthe spinal rod. In general, any process which transforms a relativelysmooth surface into a roughened surface having an increased coefficientof friction may be used. Methods for forming a roughed surface include,but are not limited to: sanding, forming grooves within a surface, ballpeening processes, electric discharge processes, and embedding of hardparticles within a surface. These processes may also be used to increasethe coefficient of friction between the fixation component and theconnector.

In an embodiment, a connector is preferably coupled to a fixationcomponent. The fixation component preferably includes a body and afixation device. The body preferably includes an upper cavity configuredto receive a connector. The fixation component preferably includes alower cavity to hold a fixation device. The fixation device preferablyincludes a head. An opening preferably extends through the centralportion of the head. A substantially cylindrical pin is preferablypositionable within the head and the body such that the fixation devicemay be rotated about pin along the longitudinal axis of the body.

The head may include two substantially flat portions. The flat portionsare formed on the head proximate the wall which divides the lower cavityfrom the upper cavity. The flat portions preferably interact with thewall to restrict rotation of the fixation device.

In an embodiment, a connector is coupled to a fixation component. Thefixation component preferably includes a body and a fixation device. Thebody preferably includes an upper cavity adapted to receive connector.The fixation device is preferably rotatable as previously described. Theconnector preferably includes a fastening end and a receiving endopposite the fastening end. The fastening end is preferably adapted toengage a fastener. The fastener is preferably a nut. The receiving endpreferably includes a pair of arms that together form a U-shapedborehole.

In an embodiment where the fastener is a nut, tightening of the fasteneris accomplished by rotating the fastener in a tightening direction. Asthe fastener is tightened, the arms are preferably deflected toward oneanother such that the slot is narrowed and the arms of the receiving endexert a compressive force against the spinal rod disposed within theborehole.

In an embodiment, fixation component preferably includes a taperedcavity for receiving connector as in the above described embodiments.The fixation system preferably includes a clip that is configured to fitabout a portion of connector. The clip is preferably configured toinhibit removal of the connector from the tapered cavity after a lockingtaper engagement is formed. The fixation component preferably includes abody and a fixation device coupled to the body. The body preferablyincludes the tapered cavity. The fixation device may be a monoaxialdevice (i.e., a non-rotatable device) or a polyaxial device (i.e.,rotatable) as described in previous embodiments. The connectorpreferably includes a fastening end and a receiving end opposite thefastening end. The receiving end preferably includes a pair of arms thattogether form a U-shaped borehole. Spinal rod is preferably positionablewithin the borehole.

The fastening end includes two indentations, formed on opposite sides ofthe fastening end. The indention is preferably formed such that thedistance between sidewalls is variable. Preferably, the distance betweensidewalls proximate the first end is substantially greater than thedistance between the sidewalls proximate the second end. In this mannerthe indentation is substantially tapered.

The indentation is configured to couple with clip to inhibit movement ofthe connector through the fixation component. The clip preferablyincludes two arms which together define a substantially U-shapedopening. Each of the arms preferably includes an upper portion and alower portion. The lower portions of each of the arms are separated fromeach other by a distance equal to or greater than the diameter of theconnector.

The clip is preferably coupled to the connector after a locking taperengagement has been formed between the connector and fixation component.The formation of the locking taper engagement preferably leaves aportion of the fastening end extending from the fixation component. Theindentation preferably is exposed when a locking taper engagement isformed. The clip is positioned such that the upper portion of the clipengages a portion of the indentation.

The clip is preferably tapered in a manner complimentary to the taperingof the indentation. As the clip is inserted through indentation, aninterference fit between the arms of the clip and the sidewalls of theindentation is preferably formed. As the clip is further inserted intothe indentation the interference fit preferably becomes stronger. Inthis manner the clip may be secured within the indentation.

In an embodiment, fixation component preferably includes a taperedcavity for receiving connector as in the above described embodiments.The connector preferably includes a tab configured to inhibit removal ofthe connector from the tapered cavity after a locking taper engagementis formed.

The tab is preferably formed proximate the top of the receiving end. Thetab preferably extends out from the outer surface of the connector. Thecavity preferably contains a channel for receiving tab. The channelpreferably has a width that is slightly larger than a width of the tab.When a locking taper engagement is formed the connector is positionedwithin the cavity such that the tab is preferably positioned within thechannel. Preferably, the tab is formed on the connector such that thetap resides within a central portion of the channel when the connectoris secured within the cavity. A bottom edge of the channel preferablyprevents further movement of the connector toward a first side of thefixation component.

An advantage of the present invention relates to a fixation componentthat may be added to or deleted from a spinal fixation construct in asurgical wound without disassembling the construct.

Another advantage of the present invention relates to a spinal fixationsystem requiring minimal assembly within the surgical wound.

Yet another advantage of the present invention relates to a spinalfixation system having a relatively narrow profile width to reduceimpingement upon the fusion mass.

BRIEF DESCRIPTION OF THE DRAWINGS

Further advantages of the present invention will become apparent tothose skilled in the art with the benefit of the following detaileddescription of the preferred embodiments and upon reference to theaccompanying drawings in which:

FIG. 1 depicts a TSRH® spinal system eyebolt assembly;

FIG. 2 depicts a side view of an embodiment of a spinal fixation systemconnected to a vertebra;

FIG. 3 depicts a top view of the spinal fixation system of FIG. 1;

FIG. 4 depicts a side view of a tapered connector constructed inaccordance with the present invention;

FIG. 5 depicts a side view of a tapered connector prior to assembly witha fixation component body and a spinal rod;

FIG. 6 depicts a side view of a tapered connector assembled with aspinal fixation component and a spinal rod;

FIG. 7 depicts a side view of a transverse connector disposed between apair of spinal rods in accordance with the present invention;

FIG. 8 depicts a front view and side view partially in section of a bonescrew constructed according to teachings of the present invention;

FIG. 9 depicts a front view and side view partially in section of a bonescrew having radially-spaced protrusions in accordance with the presentinvention;

FIG. 10 depicts a front view and a side view partially in section of areversible fixation component constructed according to teachings or thepresent invention;

FIG. 11 depicts a side view partially in section of a spacer disposedbetween a spinal rod and a fastener in accordance with the presentinvention;

FIG. 12 depicts a side view partially in section of a spinal fixationsystem prior to assembly;

FIG. 13 depicts a side view partially in section of a spinal fixationsystem assembled with an instrument;

FIG. 14 depicts a side view partially in section of a spinal fixationsystem that includes a set screw engaging a connector;

FIG. 15 depicts a spinal fixation system that includes a locking sleeve;

FIG. 16 depicts a side view of the spinal fixation system of FIG. 15after assembly;

FIG. 17 depicts a side view partially in section of the system of FIG.15 after assembly;

FIG. 18 depicts a side view of a spinal fixation system that includes arotatable fixation device;

FIG. 19 depicts a top view of a fixation component that includes arotatable fixation device;

FIG. 20 depicts a cross sectional view of the side of a spinal fixationsystem that includes a rotatable fixation device;

FIG. 21 depicts a side view of a tapered connector adapted to completelysurround a portion of a spinal rod;

FIG. 22 depicts a cross sectional view of the side of a spinal fixationsystem that includes a rotatable fixation device and a connector adaptedto completely surround a portion of a spinal rod;

FIG. 23 depicts a rear view of a spinal fixation system adapted tocompletely surround a portion of a spinal rod; and

FIG. 24 depicts a cross sectional view of the side of a spinal fixationsystem adapted to completely surround a portion of a spinal rod.

FIGS. 25a-f depict various textured patterns.

FIG. 26 depicts a cross sectional view of a spinal fixation system thatincludes a fixation component having two cavities.

FIG. 27 depicts a cross sectional view of a spinal fixation system thatincludes a fixation component having two cavities, wherein the connectoris secured to the fixation component by a fastener.

FIG. 28 depicts a perspective view of a spinal fixation system whichincludes a locking clip to secure the connector to the fixationcomponent

FIG. 29 depicts a perspective view of a connector, the connectorincluding an indentation.

FIG. 30 depicts a perspective view of a locking clip.

FIG. 31 depicts a cross-sectional view of a spinal fixation system whichincludes a connector having a locking tab.

While the invention is susceptible to various modifications andalternative forms, specific embodiments thereof are shown by way ofexample in the drawings and will herein be described in detail. Itshould be understood, however, that the drawings and detaileddescription thereto are not intended to limit the invention to theparticular form disclosed, but on the contrary, the intention is tocover all modifications, equivalents and alternatives falling within thespirit and scope of the present invention as defined by the appendedclaims.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 2 depicts a spinal fixation system 10 constructed according toteachings of the present invention. In an embodiment of the invention,spinal fixation system 10 includes a spinal rod 12 generally alignedparallel with a portion of the spine. Connector 16 secures spinalfixation components to the spinal rod via fastener 18. The fixationcomponents may include various fixation devices including bone screw 14,transverse connector 20, and spinal hooks 22 and 24.

Spinal rod 12 is preferably constructed of stainless steel or anotherrelatively rigid material. The spinal rod preferably has a substantiallycircular cross-section (although other cross-sectional geometries may beemployed) and a diameter between about ⅛ of an inch and about ¼ of aninch. The spinal rod may have a shot-peened surface to increase itsresistance to fatigue failure. The spinal rod may impart forces againstthe spine to maintain a portion of the spine in a fixed position tocorrect a spinal deformity or injury. The spinal rod may be contoured toa selected shape prior to or after surgical implantation.

Bone screw 14 is preferably inserted within the main body of a vertebra26 and may contain threads 28 to create a fixable engagement with thevertebra. Alternatively, the bone screw may have a substantially smoothshank containing no threading. The stress imparted to spinal fixationsystems resulting from a spinal deformity may cause fatigue failure of athreaded bone screw if a solid spinal fusion does not develop after aperiod of time. Threaded screws having relatively long shanks tend tofail at a location adjacent to the screw head. A substantially smooth,unthreaded shank tends to remove the stress concentration on the screwshank from a location adjacent to the screw head where failure of thescrew often occurs. The bone screw may also include a tap relief 30 tofacilitate its insertion into vertebra 26. The angle of the bone screwrelative to the spinal rod is preferably adjustable. The bone screw maybe angled to correct the angle 32 of a vertebra relative to othervertebrae in the spine. The angle between the bone screw and spinal rodis preferably fixable by tightening fastener 18. Furthermore, the heightof the vertebra 26 may be adjusted by applying a distraction force inthe directions indicated by arrow 34 between a pair of fixation devicessuch as bone screw 14 and spinal hook 24 prior to tightening fasteners18. The distraction force may be applied with the use of a tool in amanner well known to those skilled in the art.

The spinal hooks 22 and 24 may be any of a number of types of hooks wellknown to those skilled in the art including large laminar, smalllaminar, thoracic laminar, and pedicle hooks. Each spinal hook may bepositioned in the caudal direction (illustrated by hook 24 in FIG. 2) orin the cranial direction (illustrated by hook 22 in FIG. 2). Spinalhooks may be positioned on opposing sides of the spinal rod as shown inFIG. 2.

FIG. 3 depicts a top view of an embodiment of spinal fixation system 10that includes a pair of spinal rods 12 in spaced relation on each sideof the vertical axis 40 of the spine. Spinal hooks 22 and 24 arepreferably positioned for attachment to bony elements of the posteriorhuman spine. One or more transverse connectors 20 may be used to rigidlylink the rods to improve the strength of the assembly. Each of thefixation components may be attached to the spinal rod using a fastener18 that engages connector 16 and the fixation component.

Transverse connector 20 may connect neighboring rods to increase therigidity of the construct and to prevent the movement of the rodsrelative to one another. The transverse connector may be attached to thespinal rod using crosslinking plates that are well known to thoseskilled in the art and described in the TSRH® Crosslink SurgicalTechnique Manual, which is incorporated by reference herein. It ispreferred that neighboring rods be connected by two transverseconnectors that may be aligned parallel and in spaced relation from oneanother. If the spinal rod is bent, transverse connector 20 ispreferably attached to the spinal rod at a location other than the“peak” of the curved section of the rod so that additional stress is notplaced at that location.

An embodiment of connector 16 is illustrated in FIG. 4. The connectorpreferably includes a fastening end 50 and a receiving end 54 oppositethe fastening end. The fastening end may be a threaded end containingmale machine threads 52 that are adapted to engage a fastener. Thefastener is preferably a nut. The receiving end preferably includes afirst arm 56 and a second arm 58 that together form a U-shaped borehole62. The first arm has a tip 72 and the second arm has a tip 74 (eachlabeled in FIG. 5), and an opening 60 or open end is preferably definedby the tips of the first and second arm. A slot 64 preferably extendsbetween the receiving end and the fastening end. The slot may extendfrom borehole 62 proximate the receiving end to a location, proximatethe fastening end. The slot may terminate in an enlarged opening 66 asshown in FIG. 4. The borehole is preferably adapted to receive a spinalrod 12 such that the first and second arms of the receiving end surroundmore than about half of a circumferential portion of the spinal rod.

The connector preferably does not completely surround the perimeter ofthe spinal rod. The unsurrounded portion of the spinal rod is preferablyexposed from the open end 60 of the U-shaped borehole and may extendfrom the borehole through the open end. It is preferred that componentmass be placed around only slightly greater than one-half of thecircumference of the spinal rod to minimize the profile width of theconstruct. In this manner, the impingement of the construct upon thefusion mass is lessened, thereby reducing irritation of the surroundingtissue and facilitating the development of a correct spinal fusion in aminimal amount of time. Conventional assemblies tend to completelysurround the spinal rod with component mass, causing a relativelygreater impingement upon the fusion mass, which may interfere withfusion development.

The angle 68 in FIG. 4 is defined by the circumferential portion of aspinal rod that is surrounded by the first arm, second arm, and the endof slot 64. The angle 68 is preferably less than about 2 π radians(e.g., 360° around the cross-section of the spinal rod) and greater thanabout π radians (e.g., 180° around the cross-section of the spinal rod).It is preferred that more than about half of the circumferential portionthe spinal rod be surrounded by a portion of the receiving end (e.g.,first arm, second arm, end of slot 64) to allow the spinal rod to beadequately secured within the borehole. If less than half of thecircumferential portion of the spinal rod were surrounded by thereceiving end, forces resulting from spinal deformations might tend topull the spinal rod from within borehole 62. First arm 58 and second arm68 preferably engage the surface of greater than about half of thecircumferential portion of the spinal rod.

The first arm and the second arm preferably each have an outside surfacethat is slightly tapered such that the distance between the outsidesurfaces of the arms narrows in a direction from tips 72 and 74 to thefastening end 50. The taper of the outside surfaces of the armspreferably defines a locking angle 70. Locking angle 70 is preferably aconical angle, although it may be formed within a substantially flatwedge instead. Locking angle 70 is preferably less than about 30°, morepreferably less than about 25°, and more preferably still between about1° and about 20°.

FIGS. 5 and 6 illustrate the insertion of spinal rod 12 within borehole62 in an embodiment of the invention. The spinal rod is preferablyaxially positioned within the borehole by passing the spinal rod throughopening 60. Slot 64 preferably enables deflection of the first arm andthe second arm relative to one another to allow the width of opening 60to be altered. In the absence of an external force of a selectedmagnitude against the first or second arms, the width of opening 60 ispreferably less than the outside diameter 76 of the spinal rod.Receiving end 54 is preferably adapted to form a “snap-fit” engagementwith the spinal rod that may be realized by forcing the spinal rod intothe inner surfaces of tips 72 and 74 of the first and second arms,respectively. The force against the inner surfaces of the tips 72 and 74preferably causes the arms to slightly deflect in opposite directions,resulting in a slight widening of at least a portion of the slot. Inthis manner, the width of opening 60 may be increased by an amountsufficient to allow the insertion of the spinal rod through opening 60and into the borehole. Once the spinal rod is fully inserted within theborehole (as shown in FIG. 6), the arms preferably move back toward oneanother, causing the slot to narrow to its initial, unstressed width. Ifthe diameter of the spinal rod is slightly greater than that of theborehole, the arms may remain slightly deflected and the slot may remainslightly widened after the spinal rod is snapped into the borehole. Itis generally preferred that the diameter of the spinal rod and thediameter of the borehole be equal.

In an embodiment of the invention, connector 16 connects the spinal rodto a fixation component that engages a portion of the spine. Thefixation component preferably includes a fixation device such as a bonescrew, hook, transverse connector, or similar device. The fixationcomponent preferably includes a body 80 having a tapered cavity intowhich connector 16 may be inserted. The tapered cavity preferably tapersin a direction that is substantially perpendicular to the longitudinalaxis of the fixation component. The tapered cavity preferably has afirst end 84, a second end 86, and an inside surface 82. The insidesurface 82 is preferably tapered at an angle that corresponds to lockingangle 70. The tapered cavity preferably narrows in a direction fromfirst end 84 to second end 86. The tapered cavity is preferably sized sothat fastening end 50 and a portion of receiving end 54 may be insertedwithin the tapered cavity through an aperture proximate the first end.The outer width of the receiving end proximate tips 72 and 74 ispreferably slightly greater than the width of the aperture proximate thefirst end, thereby inhibiting the complete insertion of the receivingend into the tapered cavity.

Fastener 18 may be a hex nut and preferably contains female threading19, which is sized to fit the male machine threads of the fastening end50. The nut preferably engages fastening end 50 and body 80 wherebyrotating the fastener in a tightening direction creates a tensile forcein the connector in direction 88. Tightening of the fastener preferablymoves the connector within the tapered cavity in a direction from firstend 84 to second end 86, thereby creating an interference fit betweenthe arms of the receiving end and inside surface 82. As the fastener istightened, the arms are preferably deflected toward one another suchthat the slot is narrowed and the arms of the receiving end exert acompressive force against the spinal rod disposed within the borehole.

The magnitude of the compressive force exerted by the receiving end onthe spinal rod is preferably variable as a function of the degree towhich the fastener is tightened. The fastener may be selectivelytightened so that the connector is “loosely” engaged to the spinal rod.The “loose” engagement preferably fixes the position of the connector onthe rod in the absence of a selected force against the connector, whileallowing the connector to slide over the surface of the rod uponreceiving a distraction force. For instance, the fastener may bepartially tightened to loosely attach a connector and fixation deviceonto the rod at a selected location. A distraction force may be appliedto the connector to move the connector to a selected location on therod, and the fastener may then be fully tightened to maintain theconnector at the selected location.

The arms 56 and 58 preferably exert a clamping force onto “oppositesides” of the rod (i.e., sections of the outer surface of the spinal rodthat are separated by about 180°). The engagement between the arms 56and 58 and the “opposite sides” of the spinal rod preferably “centers”the rod within the borehole as shown in FIG. 6 so that substantially nogaps exist between the inner surface of the arms and the spinal rod. Therod may be constrained on opposing sides in this manner to providefurther resistance to forces that might otherwise result in axialmovement of the rod. When the arms 56 and 58 are deflected to engage thespinal rod, the receiving end preferably forms a “locking taper”engagement with the spinal rod. A “locking taper” engagement is taken tomean a largely irreversible deflection of the receiving end. That is, ifthe fastener becomes loose after the receiving end has been compressedabout the spinal rod, the clamping force exerted by the receiving endwill be maintained to fixably hold the spinal rod within the borehole.

In an embodiment of the invention depicted in FIG. 7, a transverseconnector 20 is disposed between a pair of spinal rods in spacedrelation to secure the rods at a fixed distance 90. The spinal rods arefixed within the borehole of a connector in the manner depicted in FIGS.5 and 6 and described above. The transverse connector may include abeveled surface between body 80 and a reduced section 92. Reducedsection 92 preferably has a smaller width or diameter than body 80 toallow the reduced section to be bent more easily. Slight variations indistance 39 may be achieved by bending transverse connector 20 proximatereduced section 92. The bending of the transverse connector may beaccomplished using a rod bender and a method well known to those skilledin the art. Alternately, the transverse connector may have asubstantially constant width or diameter such that the width of section92 and the width of body 80 are approximately equal.

The fixation component may include a bone screw that is used to correctthe angle 32 between vertebrae. It is preferred that the bone screw beadapted to pivot about the spinal rod to form an oblique angle betweenthe longitudinal axis of the spinal rod and the shank of the bone screw.The bone screw preferably can be pivoted in either direction 96 ordirection 98 such that an oblique angle between about 90° and about 60°is formed between the shank and the longitudinal axis of the spinal rod.Other fixation devices (e.g., hooks) may be pivoted with respect thespinal rod in the same manner. As illustrated in FIG. 8, the taperedcavity may contain an engaging side 100 adapted to contact flat 102 ofconnector 16 to limit the pivoting of a fixation device (e.g., bonescrew) about the spinal rod within a selected range, thereby preventinga gross misalignment that might complicate the assembly of the constructduring a surgical procedure.

Body 80 preferably includes a top section 104 and a bottom section 106that together form a U-shaped yoke 112 that is substantiallyperpendicular to inside surface 82 of the tapered cavity. The fixationcomponent may pivot about the spinal rod. The edges of top section 104and/or bottom section 106 may contact the spinal rod to prevent thepivoting of the fixation component about the spinal rod beyond aselected degree. Top section 104 preferably contains a curved edge 108,and bottom section 106 preferably contains a curved edge 110. Curvededges 108 and 110 preferably increase the degree that the fixationcomponent can pivot and allow a fixation device (e.g., bone screw 14) toform an angle within a selected range that is perpendicular with oroblique to the spinal rod.

In an embodiment of the invention, body 80 is laterally offset from thespinal rod. Body 80 may contain a spacer 114 that extends laterally tooffset a fixation component from the spinal rod. Offsetting a fixationcomponent from the spinal rod may reduce the degree that the spinal rodmust be contoured for proper positioning of bone screws (e.g., pediclescrews) in regions of the spine such as the lower lumbar region. Theoffset between the fixation component and the spinal rod may be equal tothe width of the spacer. The offset is preferably less than about 15 mm,more preferably less than about 10 mm, and more preferably still betweenabout 3 mm and about 9 mm.

The spacer may contain a tapered cavity for receiving connector 16 asillustrated in FIG. 9. In an embodiment, the spacer contains a firstplurality of protrusions or teeth that are adapted to form an engagementwith a second plurality of protrusions or teeth 120 disposed on asurface of a fixation device. The teeth of the spacer and the teeth ofthe fixation device preferably are radially spaced at a fixed spacing118. The teeth of the spacer and the protrusions of the fixation devicepreferably form a complementary fit such that adjacent, opposing teethcontact one another over interface length 116 when fastener 18 istightened. The complementary engagement of the teeth preferably inhibitsand/or prevents the fixation device from rotating about spacer 114,thereby fixing the angle formed between the fixation device and thespinal rod.

An embodiment including a reversible fixation device is illustrated inFIG. 10. The body 80 of the hook preferably includes a first U-shapedyoke 137 disposed on a first side 134 of the body and a second U-shapedyoke 138 disposed on a second side 136 of the body. A cavity 132preferably extends through the body from the first side 134 to thesecond side 136. The cavity preferably contains a pair of tapered innersurfaces 133 and 135 that taper in opposite directions such that thecavity narrows in a direction from the first side 134 to the middle ofthe cavity and narrows in a direction from the second side 136 to themiddle of the cavity. The tapered inner surfaces preferably eachterminate in an engaging portion 130 disposed in the middle of thecavity. Connector 16 may be positioned within the cavity so that thereceiving end extends from either first side 134 as shown in FIG. 10B orfrom second side 136 as shown in FIG. 10C. Thus, the reversible hook maybe mounted so that either first side 134 or second side 136 is proximatethe spinal rod, with the hook directed toward either the caudal orcranial direction in each case. The fixation component may contain aslot 109 through which the fastening end of the connector may beinserted during assembly of the construct. The engaging portion 130preferably engages the outer surface of the receiving end to limit theextent to which the receiving end may be inserted into cavity 132.Fastener 18 preferably engages body 80 proximate the engaging portion.

An alternate embodiment including a spacer 114 is illustrated in FIG.11. The spacer preferably surrounds a portion of connector 16 andcontains a tapered surface 140 corresponding to the outside surface ofthe arms of the receiving end. As fastener 18 is tightened, theconnector is preferably drawn within the spacer whereby surface 140engages and exerts a clamping force against the outer surface of thereceiving end. A tensile force created by the tightening of fastener 18preferably maintains the spacer in a fixed position between body 80 andthe spinal rod. The tapered surface 140 may terminate in an engagingsurface 142 that engages the receiving end, thereby limiting the extentto which the receiving end may be drawn within the spacer. The receivingend preferably forms a “pinch clamp” about the spinal rod, wherein thetips 72 and 74 of the arms terminate slightly beyond a vertical axis144, which extends through the center of the spinal rod. The fastenermay be fully tightened to create a selected offset length 145 that ispreferably between about 2 mm and about 10 mm.

To surgically install spinal fixation system 10, the threaded end ofconnector 16 is preferably inserted through the tapered cavity of aspinal fixation component and fastener 18 is loosely threaded onto thethreaded end. The spinal fixation component is then attached to thespine via a hook or screw in a selected location. A plurality of spinalfixation components may be attached to the spine in like manner. Spinalrod 11 may be contoured to match the desired curvature of the spine andplaced into the surgical opening. The spinal rod is preferably snappedwithin the borehole of the connector of each spinal fixation component.The spine is preferably manipulated such that each of the vertebra is ata selected angle and height relative to neighboring vertebrae and theneach fastener 18 is fully tightened to fixably secure the spinal rodinto the borehole of each connector and to secure each of the spinalfixation devices at a selected angle relative to the spinal rod. It isgenerally preferred that the only assembly of system components thatoccurs within the surgical wound is (a) the snapping of the spinal rodwithin one or more connectors and (b) the final tightening of one ormore fasteners that have already been engaged with the fastening end.Each of the fasteners is preferably tightened with a torque of at least150 lb-in. One or more transverse connectors may be added acrossneighboring spinal rods for support to increase the strength of theoverall construct and maintain the spinal rods at a fixed distance fromone another.

In an alternate embodiment, each connector and spinal fixation componentcan be pre-assembled on the spinal rod prior to the implantation of therod into the surgical wound. A connector may first be snapped onto thespinal rod. A fixation component may be added onto the connector suchthat the fastening end of the connector extends through the taperedcavity and the arms of the receiving end contact the inner surface ofthe tapered cavity. The fastener is preferably positioned on thefastening end and partially tightened to maintain the connector andfixation component engaged with the spinal rod. The fastener ispreferably loosely secured on the fastening end to allow the connectorand fixation component to slide along the length of the rod when aselected force is applied to the connector. The spinal rod may becontoured as necessary, and the pre-assembled system may be insertedwithin the surgical wound. The location of the spinal fixationcomponents may be adjusted along the length of the rod as necessary, andthe construct may be connected to the spine via fixation devices. Once afixation component is placed at a selected location, its correspondingfastener may be fully tightened to fix its location. Fixation componentsmay be added to or deleted from the construct as necessary withoutaltering the position of the spinal rod or other fixation components.

In an alternate embodiment, the system may be partially pre-assembledsuch that a number of connectors are initially snapped onto the spinalrod. Fixation components may be inserted within the surgical wound andconnected to the spine at selected locations via fixation devices. Therod may be selectively contoured and inserted within the surgical woundand aligned proximate the spine. A connector is preferably slid alongthe rod to a selected location proximate a fixation component on thespine, and the fastening end of the connector is inserted through thetapered cavity of the fixation component. A fastener may be placed onthe fastening end to clamp the connector onto the spinal rod and tosecure the fixation component therebetween. Additional connectors andfixation components may be secured to the spinal rod in like manner.

After the rod is implanted into the surgical wound, it may be necessaryto add or delete a fixation component. Conventional systems tend torequire that the spinal rod be removed from the surgical wound to allowa fixation component to be threaded onto or removed from the rod. Inaddition, fixation components of conventional systems may have to beremoved from the construct to slide the added fixation component to aselected position. Connector 16 is preferably snapped onto the spinalrod at a selected location. Thus, a connector and any fixationdevice.(e.g., screw, hook, transverse connector) may be added to thespinal rod without removing fixation components from the spinal rod orremoving the spinal rod from the surgical wound. In the same manner, aconnector and fixation device may be removed from the spinal rod withoutaltering the position of the spinal rod or adjacent connectors. Thefastener 18 may be loosened and a tool may be used to unclamp thereceiving end of the connector from the spinal rod, thereby eliminatingthe need to slide the component off the end of the spinal rod as in someconventional systems.

An embodiment of a spinal fixation system that is assembled with athreadless wedge is depicted in FIG. 12 and FIG. 13. FIG. 12 depicts thespinal fixation system prior to assembly. The spinal fixation systempreferably includes connector 216 for attaching spinal rod 12 tofixation component body 80. Connector 216 preferably includes areceiving end that includes a pair of deflectable arms forming asubstantially U-shaped borehole for receiving the spinal rod as in theabove described embodiments. The outer surface of the receiving end maybe tapered to complement the tapered inner surface of the cavitydisposed within the fixation component. The outer surface of thereceiving end and the tapered inner surface may be substantially flat.It is to be understood that the outer surface of the connector may beuntapered while the inner surface of the cavity is tapered, oralternatively, the outer surface of the connector may be tapered whilethe inner surface of the cavity is untapered. The end of the connectoropposite the receiving end may be capped as shown in FIG. 12.

An instrument 200 is preferably used to move the connector through thecavity to cause the arms of the connector to clamp against the spinalrod to secure it within the borehole. The instrument is preferably apair of assembly pliers that includes a first member 202 and a secondmember 204. Members 202 and 204 are preferably substantially elongatedand capable of moving relative to one another to apply a compressiveforce onto components of the spinal fixation system to assemble thecomponents. The members are preferably connected together via hinge 206.The hinge may include a pivotal connector (e.g., bolt) about which themembers can pivot relative to one another.

One of the members preferably includes an indention 210 for engaging thespinal rod. The indention preferably has a curvate shape that conformsto the shape of the spinal rod. The other member preferably includes abore 208 that is sized to receive the end of the connector. Bore 208preferably has a width that is greater than that of the end of theconnector such that the end is capable of passing into or through thebore. Member 204 preferably includes contacting sections 214 thatsurround bore 208 for engaging the fixation component. FIG. 13 depictsthe spinal fixation system after assembly. Member 202 preferably engagesthe spinal rod at indention 210, while member 204 engages the fixationcomponent with contacting sections 214. The handles of instrument 200are preferably squeezed together to decrease the distance betweenmembers 202 and 204, thereby forcing the connector to move within thecavity of the fixation component. The end of the connector preferablymoves through the cavity and into bore 208 whereby second member 204does not inhibit the movement of the connector through the cavity. Alocking taper engagement between the connector and the spinal rod ispreferably formed, and then instrument 200 may be removed from theassembly. In an alternate embodiment, member 202 engages the tips of thearms of the connector rather than the spinal rod.

In an embodiment depicted in FIG. 14, the fixation component includes abore 222 through its top surface that communicates with the fixationcomponent cavity. A locking element 220 is preferably inserted into bore222 to inhibit movement of the connector within the fixation componentcavity after the connector has been secured therein. Locking element 220is preferably a set screw. Bore 222 is preferably threaded for engagingthreads on the set screw. The locking element may engage the connectorproximate indention 218 disposed on the outer surface of the connector.

In an embodiment depicted in FIG. 15, fixation component 230 preferablyincludes a tapered cavity for receiving connector 216 as in the abovedescribed embodiments. The fixation system preferably includes a sleeve234 that is adapted to fit about the body of the fixation component. Thesleeve is preferably substantially cylindrical and may substantiallysurround the fixation component body. The sleeve preferably includes asubstantially U-shaped opening 236 sized to permit spinal rod 12 to passtherethrough. The U-shaped opening is preferably substantially offsetfrom the center of the sleeve as shown in FIG. 15. Opening 236 mayinclude an angled interior locking surface 237 for engaging the spinalrod. Fixation component 230 preferably includes a fastening end 232 onits top. Fastening end 232 preferably includes threading. A fastener 238is preferably securable to the fastening end. Fastener 238 is preferablya nut that includes threading that complements the threading on thefastening end.

FIG. 16 depicts a side view of the spinal fixation system afterassembly, and FIG. 17 depicts a cross sectional view of the assembledspinal fixation system. To assemble the system, the spinal rod ispreferably snapped into the borehole of connector 216. A circumferentialportion of the spinal rod preferably extends from the opening in theconnector. The connector having the spinal rod disposed therein is thenpreferably positioned within the cavity of the fixation component.Sleeve 234 is preferably slid over fastening end 232 and around the bodyof the fixation component until locking surface 237 contacts the spinalrod. Fastener 238 may be threaded onto the fastening end such that thebottom surface of the fastener contacts the top of sleeve 234. Rotationof the fastener preferably downwardly translates the fastener along thefastening end and forces sleeve 234 down along the body of the fixationcomponent. The angle 239 of locking surface 237 from a vertical axisallows the downward motion of the sleeve to impart a force on the spinalrod in a direction axially through the tapered cavity. Angle 239preferably ranges from about 10 to 30 degrees. The distance thatconnector 216 moves within the tapered cavity is preferably a functionof the degree to which fastener 238 is tightened. It is preferred that alocking taper engagement is formed between the connector and thefixation body cavity after fastener 238 is tightened.

In an embodiment, depicted in FIG. 18, fixation component 300 preferablyincludes a body 302 and a fixation device 304. The body 302 preferablyincludes a cavity 318 (shown in FIG. 19) adapted to receive a connector216. The body 302 may include a substantially U-shaped indentation 306adapted to permit a portion of spinal rod 12 to rest within theindentation. The indentation 306 preferably runs along the bottom 312 ofthe body 302 in a direction substantially perpendicular to thelongitudinal axis of the fixation device 304. The body 302 may include abore (not shown) that communicates with the cavity 318. A lockingelement is preferably inserted into the bore to inhibit movement of theconnector 216 within the body cavity 318 after the connector has beensecured therein.

The body 302 is preferably adapted to hold a fixation device 304. Thefixation device 304 preferably includes a head 310. The head 310 may besemi-spherical in shape. An opening (not shown) may extend through thecentral portion of the head 310, at a position equidistant from anyposition along the semi-spherical portion of the outside surface of thehead. The fixation device may a bone screw (as shown), hook, traverseconnector, or similar device. The body 302 may include a cavity 318(shown in FIG. 19) adapted to contain a portion of the head 310. Asubstantially cylindrical pin 308 is preferably positionable within thehead 310 and the body 302 such that the fixation device 304 may berotated about the pin 308 along the longitudinal axis of the body. Thepin 308 may inhibit movement of the fixation device 304 in a directionperpendicular to the longitudinal axis of the body 302. The pin 308 maybe a rivet or a screw. The pin 308 may be substantially hollow.

FIG. 19 depicts a top view of the fixation component 300. The cavity 318may be substantially U-shaped and include a front section 306 and a rearsection 308. The front section 306 is preferably adapted to receive thefixation device 304. The front section 306 preferably includes at leasttwo substantially flat arms 320 which extend out from the rear section308. The arms 320 are preferably oriented on opposing sides of the body302. The distance 322 between the two arms 320 may be substantiallygreater than the width of the head 310 of the fixation device 304. It isgenerally preferred that the distance 322 between the two arms 320 andthe width of the head 310 be equal.

In another embodiment, the head 310 of the fixation device 304 may haveat least two substantially flat edges 324. The distance 322 between thetwo arms 320 is preferably substantially the same as the width of thehead 310 between the edges 324. The edges 324 are preferably oriented onopposing sides of the head 310. The fixation device 304 may be mountedwithin the cavity 318 such that the edges 324 are contained by the arms320 of the body 302. The arms 320 may interact with the edges 324 suchthat movement in a direction perpendicular to the longitudinal axis ofthe body 302 is inhibited.

The rear section 308 of the cavity 318 is substantially rounded andadapted to receive a connector 216. FIG. 20 depicts a cross sectionalview of the fixation component 300, secured to a spinal rod 12, with aconnector 216 oriented within the rear section of the cavity. Connector216 preferably includes a receiving end that includes a pair ofdeflectable arms forming a substantially U-shaped borehole for receivingthe spinal rod, as described in previous embodiments. The width of thebody 302 between the rear side 328 and the interior surface 326 of thecavity 318 is preferably variable. The distance between the rear side328 and the interior surface 326 of the body 302 preferably becomesnarrower in a direction from the top 314 toward the bottom 312. Theinterior surface 326 of the body 302 may be substantially flat.

The head 310 of the fixation device 304 is preferably located within thebody 302 in a position such a portion of the connector 216 may beinserted between the head and the interior surface 326. Movement of theconnector 216 through the bottom 312 of the body 302, in a directiontoward the top 314, may allow the outer edges 330 of the connector toengage the interior surface 326 of the body and the head 310 of thefixation device 304. As the connector 216 is moved further toward thetop 314 of the body 302, a compressive force may be exerted by theinterior surface 326 and the head 341 upon the connector. The magnitudeof the compressive force may be varied as the position of the connector216 is varied within the cavity. The compressive force preferablysecures spinal rod 12 within the U-shaped borehole of the connector 216.The compressive force may inhibit rotation of the fixation device 304.Instrument 200 (not shown) may be used to position the connector 216within the body 302 in a position which preferably secures the spinalrod to the connector. The connector 216 may be positioned within thebody 302 such that the spinal rod 12 is secured within the connector,and the rotation of the fixation device 304 is inhibited.

FIG. 18 depicts a view of an assembled spinal fixation assembly. Toassemble the system the spinal rod 12 is snapped into the borehole ofconnector 216. A circumferential portion of the spinal rod 12 preferablyextends from the borehole in the connector 216. The connector 216 havingthe spinal rod 12 disposed therein is then preferably positioned withinthe body 302. The fixation device 304 may be rotated about the pin 308until the desired angle between the body 302 and the fixation device isachieved. The angle may be varied in a direction toward the top 314through an arc of at least 90 degrees or toward the bottom 312 throughan arc of at least 90 degrees. The connector 216 may then be movedfurther within the body 302. As the connector 216 is moved, the head 310and the interior surface 326 of the body 302 may impart a force upon theconnector (as shown in FIG. 20) causing the arms of the borehole tocompress. In this manner the connector 216 may be secured onto thespinal rod 12. The force may also inhibit further rotation of thefixation device 304. The magnitude of the force is preferably a functionof the distance that the connector 216 is placed within the body 302.Instrument 200 may be used to position the connector 216 within the body302.

An embodiment of a connector 350 is depicted in FIG. 21. The connector350 is adapted to secure fixation components to a spinal rod. Thesubstantially conical connector 350 includes a receiving section 352 andan upper section 354. The receiving section 352 preferably includes asubstantially circular opening 356. The opening 356 is preferablyadapted to receive a spinal rod (not shown) such that the receivingsection 352 of the connector 350 substantially surrounds thecircumferential portion of the spinal rod. The upper section 354preferably includes a slot 358 extending longitudinally through thecenter of the upper section. The slot 358 may extend from the top of theconnector to the opening 356, the slot communicating with the opening.

A spinal rod is preferably axially positioned within the opening 356 bypassing the spinal rod through opening. Slot 358 preferably enables thecircumference of opening 356 to be altered. Insertion of the spinal rodinto opening 356 results in a slight widening of at least a portion ofthe slot 358. In this manner, the circumference of opening 356 may beincreased by an amount sufficient to allow the insertion of the spinalrod through opening 356. If the diameter of the spinal rod is slightlygreater than that of the opening 356, the slot 358 may remain slightlywidened after the spinal rod is inserted into the opening. It isgenerally preferred that the diameter of the spinal rod and the diameterof the opening 356 be equal.

FIG. 22 depicts a cross sectional view of an assembled spinal fixationassembly including a connector 350 and a fixation component 300.Movement of the connector 350 through the bottom 312 of the body 302, ina direction toward the top 314, may allow the outer edges 360 of theconnector to engage the interior surface 326 of the body and the head310 of the fixation device 304. As the connector 350 is moved furthertoward the top 314 of the body 302, a compressive force may be exertedby the interior surface 326 and the head 310 upon the connector. Themagnitude of the compressive force may be varied as the position of theconnector 350 is varied within the cavity. The compressive forcepreferably forces slot 358 to narrow, thereby securing spinal rod 12within the opening 356 of the connector 350. The compressive force mayinhibit rotation of the fixation device 304. Instrument 200 (not shown)may be used to position the connector 350 within the body 302 in aposition which preferably secures the spinal rod 12 within theconnector. The connector 350 may be positioned within the body 302 suchthat the spinal rod 12 is secured within the connector, and the rotationof the fixation device 304 is inhibited.

To assemble the system depicted in FIG. 22 the spinal rod 12 is insertedinto the opening 356 of connector 350. A circumferential portion of thespinal rod 12 preferably is completely surrounded by the connector 350.The connector 350 having the spinal rod 12 disposed therein is thenpreferably positioned within the body 302. The fixation device 304 maybe rotated about the pin 308 until the desired angle between the body302 and the fixation device is achieved. The connector 350 may then bemoved further within the body 302. As the connector 350 is moved, thehead 310 and the interior surface 326 of the body 302 may impart a forceupon the connector causing the slot 358 of the connector to narrow. Inthis manner the connector 350 may be secured onto the spinal rod 12. Theforce may also inhibit further rotation of the fixation device 304. Themagnitude of the force is preferably a function of the distance that theconnector 350 is placed within the body 302. Instrument 200 may be usedto position the connector 350 within the body 302.

In an embodiment depicted in FIG. 23, fixation component 230 may beadapted to receive connector 350. Connector 350 preferably includes anopening 356 for receiving the spinal rod 12 and a slot 358 (shown inFIG. 24) as in the above described embodiments. The fixation component230 preferably can be pivoted in either direction 362 or direction 364such that an oblique angle between 90° and about 60° is formed betweenthe fixation component and the longitudinal axis of the spinal rod 12 asin the above described embodiments. The fixation component 230preferably comprises a bone screw (as shown), hook, traverse connector,or similar device.

To assemble the system, depicted in a cross section view in FIG. 24, thespinal rod 12 is preferably inserted into the opening 356 of connector350. The connector 350 having the spinal rod 12 disposed therein is thenpreferably positioned within the cavity of the fixation component 230.The fixation component 230 may be rotated until the desired anglebetween the fixation component and the longitudinal axis of the spinalrod is achieved. The connector 350 may then be moved further within thefixation component 230. As the connector 350 is moved, the interiorsurfaces 366 of the fixation component may impart a force upon theconnector causing the slot 358 of the connector to narrow. In thismanner the connector 350 may be secured onto the spinal rod 12. Theforce may also inhibit further rotation of the fixation component 230.The magnitude of the force is preferably a function of the distance thatthe connector 350 is placed within the body 302. Instrument 200 (notshown) may be used to position the connector 350 within the body 302.

FURTHER IMPROVEMENTS

The following improvements may be used in combination with any of thefeatures of the above-described embodiments.

Referring back to FIG. 6, the connector is shown in a locking taperengagement with the spinal rod 12. To form this locking taperengagement, the spinal rod 12 is preferably placed within opening 62such that a “snap-fit” engagement is first formed. The “snap-fit”engagement allows the connector to be moved over the surface of thespinal rod upon receiving a distraction force. The spinal rod may bemoved in a direction along the longitudinal axis of the spinal rod. Theconnector may also be moved in a direction perpendicular to thelongitudinal axis of the spinal rod. After the connector is moved to theproper position, the fastener 18 may be tightened, forcing the fixationcomponent 80 over the connector. In this manner the connector may becomefastened to the spinal rod 12 such that further movement of theconnector with respect to the spinal rod is inhibited (i.e., a lockingtaper engagement is formed). In general, fastening the connector to thespinal rod in this manner preferably inhibits movement of the connectoralong the longitudinal axis of the spinal rod and/or perpendicular tothe longitudinal axis of the spinal rod.

In an embodiment, movement of the connector with respect to the spinalrod may be further inhibited by texturing either the surface of thespinal rod or the inner surface (not shown) of the connector (i.e., thesurface of the connector that contacts the spinal rod). Preferably, bothsurfaces are textured to inhibit movement of the connector with respectto the spinal rod. During typical manufacturing procedures, the spinalrod and the inner surface of the connector may be formed as relativelysmooth surfaces. While the friction between these smooth surfaces tendsto be sufficient to maintain the connector in a fixed position upon thespinal rod, under stressful conditions the connector may be moved inresponse to the strong forces applied to the connector. By providing atextured surface, the coefficient of friction between the spinal rod andthe inner surface of the connector may be increased. This increase infriction between the spinal rod and the connector may further inhibitmovement of the connector with respect to the spinal rod. Such a systemmay be able to withstand greater distraction forces than an untexturedsystem is able to withstand. The textured components may, therefore, beless susceptible to movement after the device has been implanted withina patient.

A number of textured surfaces may be used to increase the coefficient offriction between the inner surface of the connector and the spinal rod.In general, any process which transforms a relatively smooth surfaceinto a roughened surface having an increased coefficient of friction maybe used. Methods for forming a roughened surface include, but are notlimited to sanding, forming grooves within a surface, ball peeningprocesses, electric discharge processes, and embedding of hard particleswithin a surface.

In one embodiment a plurality of grooves may be formed in the outersurface of the spinal rod or the inner surface of the connector.Preferably, a plurality of grooves is formed in both the outer surfaceof the spinal rod and the inner surface of the connector. The groovesmay be formed in a variety of patterns, depicted in FIGS. 25a-25 f. Inone embodiment, grooves may be formed in the outer surface of the spinalrod along the longitudinal axis 400 depicted in FIG. 25a. Grooves mayalso be formed in the inner surface of the connector such that thegrooves are parallel, or substantially parallel with the grooves in thespinal rod when the connector and the spinal rod are coupled together.When a textured connector and spinal rod are coupled together thelongitudinal grooves may interact with each other to provide additionalresistance to movement in a direction perpendicular to the longitudinalaxis of the spinal rod. This resistance is preferably enhanced while theconnector is fastened to the rod in a locking taper engagement asdepicted in FIG. 6. While it is preferred that both the spinal rod andthe inner surface of the connector be textured, texturing of only one ofthe surfaces may be sufficient to attain additional resistance tomovement.

Alternately, the grooves may be formed into a pattern such that thegrooves are formed perpendicular to the longitudinal axis 400 depictedin FIG. 25b. Grooves may also be formed in the inner surface of theconnector such that the grooves are parallel, or substantially parallel,with the grooves in the spinal rod when the connector and the spinal rodare coupled together. When a textured connector and spinal rod arecoupled together, the perpendicular grooves may interact with each otherto provide additional resistance to movement in a direction along thelongitudinal axis of the spinal rod. This resistance is preferablyenhanced while the connector is fastened to the rod in a locking taperengagement as depicted in FIG. 6. While it is preferred that both thespinal rod and the inner surface of the connector be textured, texturingof only one of the surfaces may be sufficient to attain additionalresistance to movement.

In general, the use of longitudinal or perpendicular texturing tends toprovide increased resistance toward movement of the connector in adirection perpendicular to the orientation of the grooves. In order toprovide increased resistance toward movement in both directions (i.e.,the longitudinal direction and a direction perpendicular to thelongitudinal direction) a variety of other patterns may be used.Diagonal patterns (FIGS. 25c and 25 d); a grid pattern (FIG. 25f) or adiamond pattern (FIG. 25e) may be formed on the contacting surfaces ofthe connector and the spinal rod to enhance the resistance to movementof the connector in both the longitudinal and the perpendiculardirections. When the connector and the spinal rod, both of which aretextured in one of the patterns depicted in FIGS. 25a 25 f are coupledtogether, the grooves may interact with each other to provide additionalresistance to movement in either a longitudinal direction or a directionperpendicular to the longitudinal axis. This resistance is preferablyenhanced while the connector is fastened to the rod in a locking taperengagement, as depicted in FIG. 6. While it is preferred that both thespinal rod and the inner surface of the connector be textured, texturingof only one of the surfaces may be sufficient to attain additionalresistance to movement. Any mixed combination of diagonal, grid ordiamond patterns may be used to increase the friction between theconnector and the spinal rod.

In another embodiment, the frictional surface may be created by anelectrical discharge process. An electrical discharge process is basedon the principle of removal of portions of a metal surface by sparkdischarges. Typically a spark is generated between the surface to betreated and an electrode by creating potential differential between thetool and the electrode. The spark produced tends to remove a portion ofthe surface disposed between the electrode and the surface. Typically,the electrode is relatively small such that only small portions of thesurface are removed. By moving the electrode about the surface numerouscavities may be formed within the surface. Typically these cavities aresomewhat pyramidal in shape. Various patterns may be formed within thesurface depending on how the electrode is positioned during thedischarge. Electric discharge machines are well known in the art. Amethod for forming a frictional surface within a metal surface using anelectric discharge process is described in U.S. Pat. No. 4,964,641 toMiesch et al. which is incorporated by reference as if set forth herein.

All of the patterns shown in FIGS. 25a-25 f may be formed using anelectric discharge machine. Preferably a diamond pattern or a wafflepattern is formed on the inner surface of the connector and/or thespinal rod. When the connector and the spinal rod, both of which aretextured by an electric discharge process, are coupled together, thegrooves may interact with each other to provide-additional resistance tomovement in either a longitudinal direction or a direction perpendicularto the longitudinal axis. While it is preferred that both the spinal rodand the inner surface of the connector be textured, texturing of onlyone of the surfaces may be sufficient to attain additional resistance tomovement. Any mixed combination of diagonal, grid or diamond patternsmay be used to increase the friction between the connector and thespinal rod.

In another embodiment, the inner surface of the connector and the outersurface of the spinal rod may be textured by the use of a shot peeningprocess. A shot peening process for forming a textured surface isdescribed in U.S. Pat. No. 5,526,664 to Vetter which is incorporated byreference as if set forth herein. In general, a shot peening processinvolves propelling a stream of hardened balls, typically made of steel,at a relatively high velocity at a surface. To create a pattern upon anarea of the surface the stream is typically moved about the surface. Thespeed by which the stream is moved about the surface tends to determinethe type of textured surface formed.

Preferably, the stream is moved such that a pattern resulting in atextured surface having ridges and valleys is formed on the innersurface of the connector and the outer surface of the spinal rod. Whenthe textured connector and spinal rod are coupled together the ridgesand valleys may interact with each other to provide additionalresistance to movement in either a longitudinal direction or a directionperpendicular to the longitudinal axis. While it is preferred that boththe spinal rod and the inner surface of the connector be textured,texturing of only one of the surfaces may be sufficient to attainadditional resistance to movement.

In another embodiment the textured surface may be produced by embeddingsharp hardened particles in the surface. A method for embedding sharphardened particles in a metal surface is described in U.S. Pat. No.4,768,787 to Shira which is incorporated by reference as if set forthherein. The method of Shira involves using a laser or other high energysource to heat the surface such that the surface melts in selectedareas. Just before the molten area re-solidifies a stream of abrasiveparticles is directed to the area. In this manner some of the particlestend to become embedded with the molten surface. The particles typicallyhave a number of sharp edges that protrude from the surface, after theparticles have been embedded within the surface. When a connector andspinal rod, textured by this process, are coupled together the hardenedparticles may interact with each other or smooth portions of the surfaceto provide additional-resistance to movement in either a longitudinaldirection or a direction perpendicular to the longitudinal axis. Whileit is preferred that both the spinal rod and the inner surface of theconnector be textured in this manner, texturing of only one of thesurfaces may be sufficient to attain additional resistance to movement.

Any of the above methods of texturing may be used in combination withanother method. For example, the outer surface of the spinal rod may betextured using a pattern of grooves. The connector, however, may betextured using an electrical discharge method. When coupled together thetextured surfaces of the connector and spinal rod may interact with eachother to provide additional resistance to movement in either alongitudinal direction or a direction perpendicular to the longitudinalaxis.

Textured surfaces may also be formed on other components of the spinalimplant system. In an embodiment, movement of the fixation componentwith respect to the spinal rod may be further inhibited by texturingeither the outer surface of the connector or the inner surface 82 of thetapered cavity of the fixation component, as depicted in FIG. 5.Preferably, both surfaces are textured to inhibit movement of thefixation component with respect to the spinal rod. In embodiments whenthe connector and the fixation component are joined without the use of afastening device, as depicted in FIG. 13, the friction between the outersurface of the connector and the inner surface of the tapered cavitypreferably prevents the fixation component from being forced away fromthe spinal rod in response to a distraction force. By providing atextured surface the coefficient of friction between the outer surfaceof the connector and the inner surface of the tapered cavity may beincreased. This increase in friction between may further inhibitmovement of the fixation component with respect to the spinal rod. Sucha system may be able to withstand greater distraction forces than anuntextured system is able to withstand. The textured components may,therefore, be less susceptible to movement after the device has beenimplanted within a patient

In another embodiment a connector 216 is disposed with a fixationcomponent having a rotatable fixation device 304 as depicted in FIG. 20.When inserted within the cavity 318 (shown in FIG. 19) connector 216exerts a force on head 310 of fixation device 304. This force may besufficient to inhibit further rotation of the fixation device. Toenhance this inhibition of the rotation of the fixation device 304,either an outer surface of connector 216 or the outer surface of head310 may be textured in one of the manners described above. Preferablyboth surfaces are textured to enhance the inhibition of rotation.

Referring to FIG. 22, connector 350 may also be textured to preventslipping of the connector with respect to the spinal rod 12. Preferablythe inner surface of opening 356 and the spinal rod are textured by anyof the methods described above. Texturing the inner surface of theopening 356 and the spinal rod 112 may provide additional resistance tomovement in either a longitudinal direction or a direction perpendicularto the longitudinal axis. Additionally, the outer surface of theconnector and the head 310 of the fixation device 304 may also betextured. Texturing of the outer surface of the connector and the head310 of the fixation device 304 may provide additional resistance torotation of the fixation device 304.

It is to be understood that any or all of the surfaces in any of theembodiments described above may textured as described. The texturing ofthe surfaces on any of the embodiments may be performed to enhanceinhibit movement of the components after assembly.

In an embodiment, depicted in FIG. 26, a connector 400 is preferablycoupled to a fixation component 450. The fixation component 450preferably includes a body 402 and a fixation device 404. The body 402preferably includes an upper cavity 408 adapted to receive connector400. The body 402 may include a bore (similar to the bore shown in FIG.14) that communicates with the upper cavity 408. A locking element maybe inserted into the bore to inhibit movement of the connector 400within the body cavity 408 after the connector has been secured therein.

The fixation component preferably includes a lower cavity 416 to hold afixation device 404. The fixation device may be a bone screw (as shown),hook, traverse connector, or similar device for securing the fixationcomponent to a bone. The fixation device 404 preferably includes a head410. The head 410 may have a number of shapes including semi-spherical,rectangular, and pyramidal. An opening 406 preferably extends throughthe central portion of the head 410. A substantially cylindrical pin 412is preferably positionable within the head 410 and the body 402 suchthat the fixation device 404 may be rotated about pin 412 along thelongitudinal axis of the body. The pin 412 may be a rivet or a screw.The pin 412 may be substantially hollow.

The head 410 may include at least one substantially flat portions.Preferably, the head includes two substantially flat portions 414 and415. The flat portions are formed on the head proximate the wall 418which divides the lower cavity 416 from the upper cavity 408. The flatportions, 414 and 415, preferably interact with the wall 418 to restrictrotation of the fixation device 404. Rotation of the fixation device 404in direction 420 preferably continues until the flat portion 414 engageswall 418. Similarly flat portion 415 engages wall 418 to restrictrotation in direction 422. Flat portions 414 and 415 of head 410 arepreferably configured to allow the fixation device to be rotated about30 degrees in either direction.

The fixation component 450 preferably includes two substantially flatarms 432 which extend out from the body in a manner similar to the armsdepicted in FIG. 19. The head 410 of the fixation device 404 preferablyhas at least two substantially flat edges. The distance between the twoarms is preferably substantially the same as the width of head 410. Thefixation device may be mounted within the lower cavity 416 such that theedges are contained by the arms 432 of the body.

Connector 400 preferably is adapted to attach a spinal rod 424 toconnect the spinal rod to the fixation component 450. Connector 400preferably includes a receiving end, the receiving end including a pairof deflectable arms 434 forming a substantially U-shaped borehole forreceiving the spinal rod 424, as described in previous embodiments. Theouter surface of the receiving end may be tapered to complement thetapered inner surface of the upper cavity 408. The outer surface of thereceiving end and the tapered inner surface may be substantially flat.It is to be understood that the outer surface of the connector may beuntapered while the inner surface of the cavity is tapered.Alternatively, the outer surface of the connector may be tapered whilethe inner surface of the cavity is untapered. The outer surface of theconnector, the inner surface of the cavity, or both of these surfacesmay be textured to inhibit loosening of the connector 400 after theconnector has been inserted within the fixation component 450. Thetexturing may be accomplished by using any of the techniques previouslydescribed.

The spinal rod 424 is preferably positioned within the U-shaped boreholeof the connector 400. To secure the spinal rod within connector 400, theconnector is preferably moved into the upper cavity 408 of the fixationcomponent 450. As connector 400 is moved within the upper cavity 408 ina direction from the first end 428 to the second end 430 an interferencefit is preferably created between the arms of the receiving end and theinner surface of the upper cavity. The arms of the receiving end arepreferably deflected toward one another such that the slot is narrowedand the arms of the receiving end exert a compressive force against thespinal rod disposed within the borehole. In this manner a locking taperengagement may be formed between the connector, the fixation device andthe spinal rod.

In an embodiment depicted in FIG. 27, a connector 400 is coupled to afixation component 450. The fixation component 450 preferably includes abody 402 and a fixation device 404. The body 402 preferably includes anupper cavity 408 adapted to receive connector 400. The fixation device404 is preferably rotatable as previously described. The connectorpreferably includes a fastening end 438 and a receiving end 436 oppositethe fastening end 438. The fastening end 438 is preferably adapted toengage a fastener 440. The fastener 440 is preferably a nut. Thereceiving end 436 preferably includes a pair of arms 434 that togetherform a U-shaped borehole.

Fastener 440 may be a hex nut and preferably contains female threading,which is sized to fit male machine threads formed on the fastening end438. The fastener 440 preferably engages fastening end 438 and body 402.Tightening of the fastener 440 preferably moves the connector within theupper cavity in a direction from first end 428 to second end 430,thereby creating an interference fit between the arms of the receivingend 436 and the inside surface of the upper cavity 408. In an embodimentwhere the fastener 440 is a nut, tightening of the fastener isaccomplished by rotating the fastener in a tightening.direction. As thefastener 440 is tightened, the arms 434 are preferably deflected towardone another such that the slot is narrowed and the arms of the receivingend 436 exert a compressive force against the spinal rod 424 disposedwithin the borehole.

In an embodiment depicted in FIG. 28, fixation component 500 preferablyincludes a tapered cavity 502 for receiving connector 550, as in theabove described embodiments. The fixation system preferably includes aclip 570 that is configured to fit about a portion of connector 550. Theclip 570 is preferably configured to inhibit removal of the connectorfrom the tapered cavity 502 after a locking taper engagement is formed.The fixation component 500 preferably includes a body 504 and a fixationdevice 506 coupled to the body. The body 504 preferably includes thetapered cavity 502. The fixation device may be a bone screw (as shown),hook, traverse connector, or similar device for securing the fixationcomponent to a bone. The fixation device may be a monoaxial device(i.e., a non-rotatable device) as shown in FIG. 28 or, alternatively,the fixation device may be polyaxial device (i.e., rotatable) asdescribed in previous embodiments.

The connector 550 preferably includes a fastening end 508 and areceiving end 510 opposite the fastening end. The receiving endpreferably includes a pair of arms 512 that together form a U-shapedborehole. Spinal rod 514 is preferably positionable within the borehole.

The fastening end 508 may include at least one indentation. Preferably,the fastening end 508 includes two indentations 516, formed on oppositesides of the fastening end. The indentation is preferably trapezoidal inshape, although other shapes may be used including square andrectangular. Turning to FIG. 29, the bottom surface and side walls 518and 520 of the indentation are preferably substantially flat. Theindention is preferably formed such that the distance between sidewalls518 and 520 is variable: Preferably, the distance between sidewalls 518and 520 proximate the first end 522 is substantially greater than thedistance between the sidewalls proximate the second end 524. In thismanner the indentation is substantially tapered.

The indentation is configured to couple with clip 570 to inhibitmovement of the connector 550 through the fixation component 500.Referring to FIG. 30, clip 570 preferably includes two arms 572 and 574which together define a substantially U-shaped opening. Each of the armspreferably includes an upper portion 578 and a lower portion 576. Thelower portion 576 of the arms has a width 580 which is substantiallyless than a width of the upper portion 578. The upper portion 578 of thearm may be substantially longer than the lower portion. The lowerportions 576 of each of the arms are separated from each other by adistance equal to or greater than the diameter of the connector 550.

The clip 570 is preferably coupled to the connector 550 after a lockingtaper engagement has been formed between the connector 550 and fixationcomponent 500. The formation of the locking taper engagement preferablyleaves a portion of the fastening end 508 extending from the fixationcomponent 500. The indentation preferably is exposed when a lockingtaper engagement is formed. To inhibit further movement of connector550, the clip 570 is positioned such that the upper portion 578 of theclip 570 engages a portion of the indentation. The clip 570 may then bepositioned such that the upper portion 578 of the clip resides withinthe indentation 516. Preferably, positioning the clip 570 isaccomplished by sliding the upper portion 578 of the clip across thebottom surface of the indentation 516. When properly positioned the topsurface 582 of clip 570 engages the upper sidewall 518 of theindentation. The lower edge 584 of the upper portion 578 of clip 570preferably engages the lower sidewall 520. The inner surface 586 of thelower portion 576 of the clip preferably engages a portion of thefastening end 508.

The clip 570 is preferably tapered in a manner complimentary to thetapering of the indentation 516. Preferably, the height 588 of clip 570is substantially greater at the first end 590 than a height of the clipat the second end 592. The height 588 of the clip proximate the firstend 590 is preferably slightly greater than a width of the indentationproximate end 522. As the clip 570 is inserted through indentation 516,an interference fit between the arms 572 and 574 of the clip and thesidewalls 518 and 522 of the indentation is preferably formed. As theclip is further inserted into the indentation the interference fitpreferably becomes stronger. In this manner the clip may be securedwithin the indentation.

In an embodiment, depicted in FIG. 31, fixation component 600 preferablyincludes a tapered cavity 602 for receiving connector 650 as in theabove described embodiments. The connector 650 preferably includes a tab620 configured to inhibit removal of the connector from the taperedcavity 502 after a locking taper engagement is formed. A tab as usedherein is defined as a protrusion of any shape which extends out from asurface of a component. The fixation component preferably includes abody 604 and a fixation device 606 coupled to the body. The body 604preferably includes the tapered cavity 602. The fixation device 606 maybe a bone screw (as shown), hook, traverse connector, or similar devicefor securing the fixation component to a bone. The fixation device 606may be a monoaxial device (i.e., a non-rotatable device) or,alternatively, the fixation device may be polyaxial device (i.e.,rotatable) as shown in FIG. 31.

The connector 650 preferably includes a fastening end 608 and areceiving end 610 opposite the fastening end. The receiving endpreferably includes a pair of arms 612 that together form a U-shapedborehole. Spinal rod 614 is preferably positionable within the borehole.

The tab 620 is preferably formed proximate the top of the receiving end610. The tab may have a number of shapes including but not limited torectangular, square, diamond, and triangular. Preferably, the tab isrectangular in shape. The tab 620 preferably extends out from the outersurface of the connector 550. The tab may extend over about half of thecircumference of the connector. Preferably, the tab 620 extends overless than about a quarter of the circumference of the connector. Asecond tab (not shown) may be formed opposite the first tab.

The cavity 602 preferably contains a channel 622 for receiving tab 620.The channel 622 may be formed in either the rear wall 624 of the cavity602 or the front wall 626 of the cavity. The channel 622 may be formedin both the front and rear portions of the cavity. The channelpreferably has a width that is slightly larger than a width of the tab.When a locking taper engagement is formed the connector is positionedwithin the cavity such that the tab is preferably positioned within thechannel. Preferably, the tab is formed on the connector such that thetap resides within a central portion of the channel, as depicted in FIG.31, when the connector 650 is secured within the cavity 602. Theconnector 602 may be moved in a direction toward the first side 628 ofthe fixation component until the tab 620 engages the bottom edge 630 ofthe channel 622. The bottom edge 630 of the channel preferably preventsfurther movement of the connector toward first side 628. The bottom edgeof the channel is preferably positioned to allow the connector to bepartially moved toward the first side 628. Movement of the connectortoward the first side will preferably reduce the pressure exerted by theconnector upon the spinal rod. This allows the spinal rod to berepositioned within the connector without having to remove the connectorfrom the cavity. A nut or locking clip 640 may be attached to thefastening end of the connector to inhibit removal of the connector fromthe tapered cavity 502 after a locking taper engagement is formed.

It is to be understood that any or all of the surfaces in any of theembodiments depicted in FIGS. 26-31 may textured as described above. Thetexturing of the surfaces on any of the embodiments may be performed toenhance inhibit movement of the components after assembly.

Further modifications and alternative embodiments of various aspects ofthe invention will be apparent to those skilled in the art in view ofthis description. Accordingly, this description is to be construed asillustrative only and is for the purpose of teaching those skilled inthe art the general manner of carrying out the invention. It is to beunderstood that the forms of the invention shown and described hereinare to be taken as the presently preferred embodiments. Elements andmaterials may be substituted for those illustrated and described herein,parts and processes may be reversed, and certain features of theinvention may be utilized independently, all as would be apparent to oneskilled in the art after having the benefit of this description of theinvention. Changes may be made in the elements described herein withoutdeparting from the spirit and scope of the invention as described in thefollowing claims.

What is claimed is:
 1. A connector for connecting spinal fixationcomponents to a spinal rod, comprising: a lower section, the lowersection comprising a first arm and a second arm that form an opening forreceiving the spinal rod, and wherein portions of surfaces of the firstarm and the second arm that define the opening comprise non-threaded,textured surfaces configured to have large coefficients of friction withrespect to the spinal rod; an upper section, the upper section defininga slot communicating with the opening in the lower section, wherein theslot terminates in an enlarged opening in the upper section; and whereinthe arms are deflectable to cause widening of a portion of the slot andwidening of a width of the opening to allow the spinal rod to be placedinto the opening, and wherein the arms are deflectable to causenarrowing of a portion of the slot and narrowing of the width of theopening to allow for frictional engagement of the spinal rod by thenon-threaded, textured surfaces of the first arm and second arm duringuse to inhibit movement of the connector with respect to the spinal rod.2. The connector as defined in claim 1, further comprising at least oneindentation in the upper section configured to attach the connector to afixation component.
 3. The connector as defined in claim 1, furthercomprising threading on the upper section configured to attach theconnector to a fixation component.
 4. The connector as defined in claim1, further comprising a fastener configured to couple the connector to afixation component during use.
 5. The connector as defined in claim 1,the width of the opening before the arms are deflected is less than adiameter of the spinal rod.
 6. The connector as defined in claim 1,wherein the non-threaded, textured surfaces are configured to contact aportion of the spinal rod during use, and wherein the non-threaded,textured surfaces are configured to inhibit motion of the spinal rodduring use.
 7. The connector as defined in claim 1, wherein theconnector further comprises a pair of tapered sides, and wherein a widthbetween the sides is greatest near the opening and least near a top ofthe upper section.
 8. The connector as defined in claim 7, wherein aportion of outer surfaces of the pair of sides comprise texturing. 9.The connector as defined in claim 8, wherein the textured outer surfacesare prepared by forming a plurality of grooves in the surfaces.
 10. Theconnector as defined in claim 8, wherein the textured outer surfaces areprepared by a shot peening process.
 11. The connector as defined inclaim 8, wherein the textured outer surfaces are prepared by an electricdischarge process.
 12. The connector as defined in claim 1, whereinouter surfaces of the first and second arms taper, wherein a widthbetween the first arm and the second arm is greatest near the openingand least near a bottom of the upper section, and wherein the uppersection comprises a protrusion configured to fit within a cavity of afixation component.
 13. The connector as defined in claim 1, wherein thenon-threaded, textured surfaces are prepared by forming a plurality ofgrooves in the opening.
 14. The connector as defined in claim 1, whereinthe non-threaded, textured surfaces are prepared by a shot peeningprocess.
 15. The connector as defined in claim 1, wherein thenon-threaded, textured surfaces are prepared by an electric dischargeprocess.
 16. The connector as defined in claim 1, further comprising aspacer configured to fit between the lower section and a fixationcomponent during use.
 17. The connector as defined in claim 16, whereinthe fixation component further comprises a fixation device, wherein thefixation device comprises protrusions, and wherein the spacer furthercomprises teeth configured to form a complementary engagement with theprotrusions to inhibit rotation of the fixation device about the spacerduring use.
 18. The connector as defined in claim 1, further comprisinga fixation component having a cavity, wherein a portion of the lowersection fits within the cavity.
 19. The connector as defined in claim18, wherein walls of the fixation component that form the cavity areconfigured to compress the first arm and the second arm to secure thefixation component to the connector and the connector to the spinal rodduring use.
 20. The connector as defined in claim 18, wherein a portionof outer surfaces of walls that form the cavity are textured.
 21. Theconnector as defined in claim 18, wherein the fixation component furthercomprises a hole, and further comprising a locking element configured toextend through the hole and contact the connector to inhibit movement ofthe connector within the cavity during use.
 22. The connector as definedin claim 21, further comprising at least one indentation in the uppersection, wherein the locking element engages the at least oneindentation during use.
 23. The connector as defined in claim 18,wherein the fixation component further comprises a fixation device forattaching the spinal rod to a vertebra.
 24. The connector as defined inclaim 18, wherein the fixation component comprises a top section and abottom section, wherein the top section and the bottom section eachcomprise at least one curved edge, and wherein the fixation component isconfigured to pivot about the spinal rod in a substantially verticalplane during use, and wherein curved edges of the top section and thebottom section are configured to contact the spinal rod during pivotingof the fixation component to define a range of pivotal motion of thefixation component during use.
 25. The connector as defined in claim 18,wherein the fixation component further comprises a transverse connectorfor coupling the spinal rod to a neighboring spinal rod.
 26. Theconnector as defined in claim 18, wherein the fixation component furthercomprises a fixation device, the fixation device comprising a head,wherein the head is configured to be positionable within the cavity sothat the fixation device is rotatable about a longitudinal axis of thespinal rod during use, and wherein a surface of the head issubstantially textured so that the textured surface of the headinteracts with an outer surface of the connector to inhibit rotation ofthe fixation device during use.
 27. A connector for attaching spinalfixation components to a spinal rod, comprising: an upper section; afirst arm extending from the upper section, the first arm comprising anon-threaded, textured surface configured to frictionally engage anouter surface of the spinal rod; a second arm extending from the uppersection, the second arm comprising a surface configured to engage theouter surface of the spinal rod; a slot in the upper section between thefirst arm and second arm, the slot extending to a bottom of the uppersection and terminating in an enlarged opening in the bottom of theupper section; and an opening between the surface of the first arm andthe surface of the second arm, the opening configured to receive thespinal rod, wherein the first arm and second arm are deflectable tocause the slot to narrow, which fixes the spinal rod within the openingduring use.
 28. The connector as defined in claim 27, further comprisingat least one indentation in the upper section configured to attach theconnector to a fixation component.
 29. The connector as defined in claim27, further comprising threading on the upper section configured toattach the connector to a fixation component.
 30. The connector asdefined in claim 27, further comprising a fastener configured to couplethe connector to a fixation component during use.
 31. The connector asdefined in claim 27, wherein the width of the opening before the armsare deflected is less than a diameter of the spinal rod.
 32. Theconnector as defined in claim 27, wherein the connector furthercomprises a pair of tapered sides, and wherein a width between the sidesis greatest near the opening and least near a top of the upper section.33. The connector as defined in claim 32, wherein a portion of outersurfaces of the pair of tapered sides comprise texturing.
 34. Theconnector as defined in claim 33, wherein the textured outer surfacesare prepared by forming a plurality of grooves in the surfaces.
 35. Theconnector as defined in claim 33, wherein the textured outer surfacesare prepared by a shot peening process.
 36. The connector as defined inclaim 33, wherein the textured outer surfaces are prepared by anelectric discharge process.
 37. The connector as defined in claim 27,wherein outer surfaces of the first and second arms taper, wherein awidth between the first arm and the second arm is greatest near theopening and least near a bottom of the upper section, and wherein theupper section comprises a protrusion configured to fit within a cavityof a fixation component.
 38. The connector as defined in claim 27, thetextured surface is prepared by forming a plurality of grooves in theopening.
 39. The connector as defined in claim 27, wherein the texturedsurface is prepared by a shot peening process.
 40. The connector asdefined in claim 27, wherein the textured surface is prepared by anelectric discharge process.
 41. The connector as defined in claim 27,further comprising a spacer configured to fit between the upper sectionand a fixation component during use.
 42. The connector as defined inclaim 35, wherein the fixation component further comprises a fixationdevice, wherein the fixation device comprises protrusions, and whereinthe spacer further comprises teeth configured to form a complementaryengagement with the protrusions to inhibit rotation of the fixationdevice about the spacer during use.
 43. The connector as defined inclaim 27, further comprising a fixation component having a cavity,wherein a portion of the upper section fits within the cavity.
 44. Theconnector as defined in claim 43, wherein walls of the fixationcomponent that form the cavity are configured to compress the arms ofthe connector to secure the fixation component to the connector and theconnector to the spinal rod during use.
 45. The connector as defined inclaim 43, wherein a portion of outer surfaces of walls that form thecavity are textured.
 46. The connector as defined in claim 43, whereinthe fixation component further comprises a hole, and further comprisinga locking element configured to extend through the hole and contact theconnector to inhibit movement of the connector within the cavity duringuse.
 47. The connector as defined in claim 46, further comprising atleast one indentation in the upper section, wherein the locking elementengages the at least one indentation during use.
 48. The connector asdefined in claim 43, wherein the fixation component further comprises afixation device for attaching the spinal rod to a vertebra.
 49. Theconnector as defined in claim 43, wherein the fixation componentcomprises a top section and a bottom section, wherein the top sectionand the bottom section each comprise at least one curved edge, andwherein the fixation component is configured to pivot about the spinalrod in a substantially vertical plane during use, and wherein curvededges of the top section and the bottom section are configured tocontact the spinal rod during pivoting of the fixation component todefine a range of pivotal motion of the fixation component during use.50. The connector as defined in claim 43, wherein the fixation componentfurther comprises a transverse connector for attaching the spinal rod toa neighboring spinal rod.
 51. The connector as defined in claim 43,wherein the fixation component further comprises a fixation device, thefixation device comprising a head, wherein the head is configured to bepositionable within the cavity so that the fixation device is rotatableabout a longitudinal axis of the spinal rod during use, and wherein asurface of the head is substantially textured so that the texturedsurface of the head interacts with an outer surface of the connector toinhibit rotation of the fixation device during use.
 52. A connector forattaching spinal fixation components to a spinal rod, comprising: abody; an opening through the body defining a surface; non-threadedtexturing on a portion of the surface that forms a non-threaded texturedsurface, the non-threaded textured surface configured to frictionallyengage a spinal rod during use to inhibit movement of the spinal rodrelative to the body; and a longitudinal slot in the body, wherein afirst end of the slot is in communication with the opening through thebody and a second end of the slot terminates in an enlarged secondopening, wherein narrowing the slot fixes a spinal rod positioned withinthe opening to the connector, and wherein widening the slot allows thespinal rod positioned within the opening to be removed from the opening.53. The connector as defined in claim 52, wherein the textured surfaceis prepared by forming a plurality of grooves in the surface.
 54. Theconnector as defined in claim 52, wherein the textured surface isprepared by a shot peening process.
 55. The connector as defined inclaim 52, wherein the textured surface is prepared by an electricdischarge process.
 56. The connector as defined in claim 52, furthercomprising at least one indentation in the body configured to attach theconnector to a fixation component.
 57. The connector as defined in claim52, further comprising threading on a portion of the body, the threadingconfigured to attach the connector to a fixation component.
 58. Theconnector as defined in claim 52, further comprising a fastenerconfigured to couple the connector to a fixation component during use.59. The connector as defined in claim 52, wherein the portion of theouter surface of the spinal rod comprises a textured surface.
 60. Theconnector as defined in claim 52, wherein the body further comprises apair of tapered sides, and wherein a width between the sides is greatestnear the top of the body and least near the bottom of the body.
 61. Theconnector as defined in claim 60, wherein a portion of outer surfaces ofthe pair of tapered sides comprise texturing.
 62. The connector asdefined in claim 61, wherein the textured outer surfaces are prepared byforming a plurality of grooves in the surfaces.
 63. The connector asdefined in claim 61, wherein the textured outer surfaces are prepared bya shot peening process.
 64. The connector as defined in claim 61,wherein the textured outer surfaces are prepared by an electricdischarge process.
 65. The connector as defined in claim 52, whereinouter surfaces of the body taper, wherein a width between outer surfacesof the body is greatest near the top of the body and least near thebottom of the body, and wherein a portion of the body is configured tofit within a cavity of a fixation component.
 66. The connector asdefined in claim 52, further comprising a spacer configured to fitbetween the opening and a fixation component during use.
 67. Theconnector as defined in claim 66, wherein the fixation component furthercomprises a fixation device, wherein the fixation device comprisesprotrusions, and wherein the spacer further comprises teeth configuredto form a complementary engagement with the protrusions to inhibitrotation of the fixation device about the spacer during use.
 68. Theconnector as defined in claim 52, further comprising a fixationcomponent having a cavity, wherein a portion of the body fits within thecavity.
 69. The connector as defined in claim 68, wherein walls of thefixation component that form the cavity are configured to compress thearms of the connector to secure the fixation component to the connectorand the connector to the spinal rod during use.
 70. The connector asdefined in claim 68, wherein a portion of outer surfaces of walls thatform the cavity are textured.
 71. The connector as defined in claim 68,wherein the fixation component further comprises a hole, and furthercomprising a locking element configured to extend through the hole andcontact the connector to inhibit movement of the connector within thecavity during use.
 72. The connector as defined in claim 71, furthercomprising at least one indentation in the body, wherein the lockingelement engages the at least one indentation during use.
 73. Theconnector as defined in claim 68, wherein the fixation component furthercomprises a fixation device for attaching the spinal rod to a vertebra.74. The connector as defined in claim 68, wherein the fixation componentcomprises a top section and a bottom section, wherein the top sectionand the bottom section each comprise at least one curved edge, andwherein the fixation component is configured to pivot about the spinalrod in a substantially vertical plane during use, and wherein curvededges of the top section and the bottom section are configured tocontact the spinal rod during pivoting of the fixation component todefine a range of pivotal motion of the fixation component during use.75. The connector as defined in claim 68, wherein the fixation componentfurther comprises a transverse connector for coupling the spinal rod toa neighboring spinal rod.
 76. The connector as defined in claim 68,wherein the fixation component further comprises a fixation device, thefixation device comprising a head, wherein the head is configured to bepositionable within the cavity so that the fixation device is rotatableabout a longitudinal axis of the spinal rod during use, and wherein asurface of the head is substantially textured so that the texturedsurface of the head interacts with an outer surface of the connector toinhibit rotation of the fixation device during use.
 77. A connector forattaching spinal fixation components to a spinal rod, comprising: abody; an opening through the body defining a surface; texturing on aportion of the surface that forms a textured surface, the texturedsurface configured to frictionally engage a spinal rod during use toinhibit movement of the spinal rod relative to the body; a longitudinalslot in the body in communication with the opening, wherein narrowingthe slot fixes a spinal rod positioned within the opening to theconnector, and wherein widening the slot allows the spinal rodpositioned within the opening to be removed from the opening; a pair oftapered sides, wherein at least a portion of outer surfaces of the pairof sides comprises texturing; and at least one indentation in the bodyconfigured to accept a clip that couples the connector to a fixationcomponent.
 78. The connector as defined in claim 77, further comprisinga spacer configured to fit between the opening, and a fixation componentduring use.
 79. The connector as defined in claim 77, further comprisinga fixation component having a cavity, wherein a portion of the body fitswithin the cavity.